checkout-index: add parallel checkout support

Allow checkout-index to use the parallel checkout framework, honoring
the checkout.workers configuration.

There are two code paths in checkout-index which call
`checkout_entry()`, and thus, can make use of parallel checkout:
`checkout_file()`, which is used to write paths explicitly given at the
command line; and `checkout_all()`, which is used to write all paths in
the index, when the `--all` option is given.

In both operation modes, checkout-index doesn't abort immediately on a
`checkout_entry()` failure. Instead, it tries to check out all remaining
paths before exiting with a non-zero exit code. To keep this behavior
when parallel checkout is being used, we must allow
`run_parallel_checkout()` to try writing the queued entries before we
exit, even if we already got an error code from a previous
`checkout_entry()` call.

However, `checkout_all()` doesn't return on errors, it calls `exit()`
with code 128. We could make it call `run_parallel_checkout()` before
exiting, but it makes the code easier to follow if we unify the exit
path for both checkout-index modes at `cmd_checkout_index()`, and let
this function take care of the interactions with the parallel checkout
API. So let's do that.

With this change, we also have to consider whether we want to keep using
128 as the error code for `git checkout-index --all`, while we use 1 for
`git checkout-index <path>` (even when the actual error is the same).
Since there is not much value in having code 128 only for `--all`, and
there is no mention about it in the docs (so it's unlikely that changing
it will break any existing script), let's make both modes exit with code
1 on `checkout_entry()` errors.

Signed-off-by: Matheus Tavares <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: matheustavares

builtin/checkout-index.c

@@ -12,6 +12,7 @@
 #include "cache-tree.h"
 #include "parse-options.h"
 #include "entry.h"
+#include "parallel-checkout.h"
 
 #define CHECKOUT_ALL 4
 static int nul_term_line;
@@ -115,7 +116,7 @@ static int checkout_file(const char *name, const char *prefix)
 	return -1;
 }
 
-static void checkout_all(const char *prefix, int prefix_length)
+static int checkout_all(const char *prefix, int prefix_length)
 {
 	int i, errs = 0;
 	struct cache_entry *last_ce = NULL;
@@ -142,11 +143,7 @@ static void checkout_all(const char *prefix, int prefix_length)
 	}
 	if (last_ce && to_tempfile)
 		write_tempfile_record(last_ce->name, prefix);
-	if (errs)
-		/* we have already done our error reporting.
-		 * exit with the same code as die().
-		 */
-		exit(128);
+	return !!errs;
 }
 
 static const char * const builtin_checkout_index_usage[] = {
@@ -182,6 +179,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	int force = 0, quiet = 0, not_new = 0;
 	int index_opt = 0;
 	int err = 0;
+	int pc_workers, pc_threshold;
 	struct option builtin_checkout_index_options[] = {
 		OPT_BOOL('a', "all", &all,
 			N_("check out all files in the index")),
@@ -236,6 +234,10 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 		hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 	}
 
+	get_parallel_checkout_configs(&pc_workers, &pc_threshold);
+	if (pc_workers > 1)
+		init_parallel_checkout();
+
 	/* Check out named files first */
 	for (i = 0; i < argc; i++) {
 		const char *arg = argv[i];
@@ -275,12 +277,16 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 		strbuf_release(&buf);
 	}
 
+	if (all)
+		err |= checkout_all(prefix, prefix_length);
+
+	if (pc_workers > 1)
+		err |= run_parallel_checkout(&state, pc_workers, pc_threshold,
+					     NULL, NULL);
+
 	if (err)
 		return 1;
 
-	if (all)
-		checkout_all(prefix, prefix_length);
-
 	if (is_lock_file_locked(&lock_file) &&
 	    write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 		die("Unable to write new index file");